CN116183036A - Method for correcting background radiation response of short wave infrared band of polarized remote sensor - Google Patents

Abstract

The invention discloses a method for correcting background radiation response of a polarized remote sensor in a short wave infrared band, which comprises the following steps: firstly, establishing a remote sensor response function according to the absolute spectral responsivity, target spectral radiance and background radiation of the remote sensor; dividing the test temperature into a plurality of temperature levels, and obtaining a background radiation response by adopting polynomial fitting; measuring background radiation responsivity by using an integrating sphere and a vacuum high-low temperature environment simulation test system to obtain equivalent blackbody temperature; obtaining corresponding in-band weight radiance by utilizing the ratio of the background radiation response signal to the background radiation equivalent spectral responsivity at the known reference temperature; calculating the total response of the background radiation by using the estimated weight spectrum radiance and the instrument internal radiation equivalent spectral responsivity; and analyzing the correction precision of the polarization response of the background radiation by adopting a synthetic uncertainty evaluation method. The invention can be used for eliminating background radiation, increasing the dynamic range of a detection system and improving the signal-to-noise ratio and measurement accuracy of the system.

Description

A correction method for background radiation response in short-wave infrared band of polarization remote sensor

technical field

The invention relates to the technical field of remote sensor calibration data processing, in particular to a correction method for background radiation response in the short-wave infrared band of a polarization remote sensor.

Background technique

In recent years, driven by the international demand for earth observation, atmospheric detection, planetary detection and other fields, polarization remote sensing detection technology has entered the stage of wide spectral coverage, large dynamic range observation, and high-precision detection. In order to achieve effective detection of long-distance and weak targets, high-sensitivity cooling infrared detectors are often used, which are particularly sensitive to heat sources, and the impact of background radiation on the system is more prominent, and the polarization response characteristics caused by it are difficult to ignore. It affects the efficiency and accuracy of polarization calibration, and has become a bottleneck that limits the improvement of calibration accuracy in the short-wave infrared band of polarization remote sensors.

Background radiation usually refers to the radiant energy of non-observation targets received by the instrument detection system. The background radiation will directly lead to the increase of the background noise of the polarization remote sensor in the short-wave infrared band and the drift of the dynamic range, thus affecting the response measurement value of the polarization remote sensor. The influence of background radiation on infrared detection becomes more obvious with the weakening of target signal and the improvement of detector performance. Although the radiation response of the infrared channel detector in the normal temperature range is almost linear, according to the research, the infrared channel has obvious nonlinear characteristics at the low-temperature end and high-temperature end in the vacuum calibration state, and accurate target calibration at the low-temperature end is very important for cloud microspheres. Physical parameter inversion is very important. In earth observation and space weak target detection, the target radiation is weak and the response of the detector is low. At this time, the background radiation becomes the dominant factor restricting the improvement of the signal-to-noise ratio and polarization measurement accuracy of the system in the short-wave infrared band.

Compared with the visible light system, the short-wave infrared system adopts the working method of passively accepting the thermal radiation of the target, so the background radiation characteristics of the system are more complicated, including not only the external background radiation, but also the stray radiation generated by the system's own structure, that is, the internal background radiation. The source of internal background radiation is relatively complex. According to the type of radiation source, the source of internal background radiation can be roughly divided into three categories: optical components, structural components, and background radiation of the uncooled part of the detector. The surface of optical components and mechanical structures, as well as the uncooled part of the detector will generate thermal radiation, which will be received by the detector after multiple reflections, refraction or diffraction. The radiation of optical components is mainly related to factors such as material type and temperature. The radiation of mechanical structures is mainly related to factors such as material emissivity, temperature, and transmission path. The radiation of the uncooled part of the detector is mainly related to factors such as material type and temperature.

According to the analysis of background radiation research at home and abroad, the current research methods for detecting system background radiation mainly include software modeling analysis method and BAT (built-and-test) method. The software modeling analysis method refers to modeling the generation process of the background radiation signal according to the principles of infrared physics, quantifying various factors that affect the radiation characteristics of the target, and simulating the background radiation signals in different environments. At present, there are mainly Monte Carlo methods , ray tracing method, area method, etc. Because the method is low in cost, not limited by equipment and test site conditions, it can realize accurate and detailed analysis at the system level and component level at the same time, and has been widely used. Its disadvantage is that its accuracy and effectiveness cannot be verified. In fact, the on-site environment is much more complicated than the simulated environment, and it is impossible to obtain accurate target radiation characteristics through simulation.

For the measurement of the background radiation response, the BAT method is mainly used, that is, to establish a measurement model of the infrared radiation characteristics of the target, and to test and correct the model through the on-site radiation measurement test. This is the most direct means to obtain the real radiation characteristics of the target. A relatively complete measurement system has been formed abroad. For example, the Arnold Center in Tennessee, California, USA, accurately measures the background radiation of the infrared system under low temperature conditions and a vacuum environment. However, this experimental testing method is very difficult to implement, and the error is also large.

At present, domestic research on background radiation is mainly based on simulation analysis, and a perfect background radiation measurement system has not yet been established. One of the few domestic research reports based on experimental methods, Chang Songtao et al., Changchun Institute of Optics and Mechanics, Chinese Academy of Sciences, proposed a method for measuring the internal background radiation of a cooling infrared system based on the principle of radiation calibration. By calibrating the infrared detector combined with the radiation calibration of the infrared system As a result, the internal background radiation of the system is solved, but this method does not carry out quantitative analysis on the background radiation.

Contents of the invention

In order to overcome the defects of the prior art and solve the problem of the increase of the background noise in the short-wave infrared band of the polarization remote sensor and the drift of the dynamic range caused by the background radiation, the present invention provides a method for correcting the response of the background radiation in the short-wave infrared band of the polarization remote sensor to realize the polarization remote sensor Accurate measurement and correction of background radiation in the short-wave infrared band, reducing the impact of background radiation on the measurement results in the short-wave infrared band.

The present invention is achieved through the following technical solutions:

A method for correcting the background radiation response in the short-wave infrared band of a polarization remote sensor, comprising the following steps:

Step (1), according to the relationship between the short-wave infrared band response of the polarization remote sensor and its absolute spectral responsivity R(λ _k ), the target spectral radiance L(λ _k ), and the background radiation response F _bkg (λ _k ), the polarization The response function S(λ _k ) of the remote sensor;

In step (2), the test temperature of each channel of the polarization remote sensor is divided into multiple temperature levels, and polynomial fitting is used to obtain the background radiation response of each channel;

Step (3), using the spectrally adjustable integrating sphere as the reference light source and the vacuum high and low temperature environment simulation test system to measure the background radiation response, using the spectrally adjustable integrating sphere as the reference light source to radiate the internal radiation of the simulated instrument to obtain the equivalent black body temperature;

Step (4), using multiple temperature points of the vacuum high and low temperature environment simulation test system, under the condition of a known reference temperature, obtain the ratio of the background radiation response signal at the known reference temperature to the equivalent spectral responsivity of the background radiation Corresponding in-band weighted radiance L _m (λ _j );

Step (5), using the estimated weighted spectral radiance and the equivalent spectral responsivity of the internal radiation of the instrument to calculate the total background radiation response F _bkg (λ);

In step (6), the correction accuracy of the polarization response of the background radiation is analyzed by using the composite uncertainty evaluation method.

Further, in the step (1), the response function S(λ _k ) of the polarization remote sensor is:

Among them, λ _k is the kth channel of the polarization remote sensor wavelength λ, k is the channel number of the polarization remote sensor, λ _min and λ _max are the shortest and longest wavelengths that the polarization remote sensor has response, L(λ _k ) is the wavelength λ The spectral radiance of the k-th channel, R(λ _k ) is the absolute spectral responsivity of the k-th channel at wavelength λ, and F _bkg (λ _k ) is the background radiation response of the k-th channel of the polarization remote sensor at wavelength λ.

Further, in the step (2), the background radiation response of each polarization channel of the polarization remote sensor is divided into multiple temperature levels, and the background radiation response when the temperature is t _i is represented by F _bkg (λ _k , t _i ):

Among them, L _Int (λ _k ,t _i ) is the spectral radiance of the internal radiation of the instrument, R(λ _k ,t ₀ ) is the absolute spectral responsivity at the initial temperature point t ₀ , B _i is the fitting coefficient, t _i is the temperature point, and i is the number of the temperature point.

即辐射值；然后，将/>

按对应波段积分，获得该波段积分能量；最后，利用插值方法估算同等能量的黑体温度，如式(3)所示：Further, the step (3) includes: firstly, according to the original spectrum S _DS observed in the cold space, that is, the count value and the instrument spectral response function R(λ _k ), approximately calculate the equivalent spectral responsivity of the internal radiation of the instrument

i.e. the radiation value; then, the />

Integrate according to the corresponding band to obtain the integral energy of the band; finally, use the interpolation method to estimate the blackbody temperature of the same energy, as shown in formula (3):

Among them, S _DS and S _ICT represent the output signal of the instrument when the cold space and the reference light source are incident, respectively, L _ICT represents the spectral radiance of the inner black body, R(λ _k ) is the spectral response function of the instrument, and <·> represents the mean value.

Further, the step (4) includes: dividing the working environment temperature of the kth channel of the polarization remote sensor into multiple temperature levels according to the change of the actual working environment temperature, assuming that the temperature t _{j at the temperature point j} is a known reference temperature , the ratio of the polarization remote sensor background radiation response signal F(λ _k ,t _j ) to the background radiation equivalent spectral responsivity δ _bkg (λ _k ,t _j ) at temperature t _j and the in-band weighted radiance corresponding to the mth channel L _m (λ _j ) are approximately equal, as shown in formula (4):

Further, in the step (5), the total background radiation response F _bkg (λ _k ) is composed of the weighted radiance L _m (λ _j ) and background radiation responsivity δ _bkg (λ _k ) corresponding to all known temperature points ,t _j ), as shown in formula (5):

Further, in the step (6), according to the measurement method of the background radiation and the mathematical model B=f(x ₁ , x ₂ ... x _n ), determine the uncertainty _u (x _i ) and its propagation rate, the correction accuracy of the background radiation polarization response is analyzed by the composite uncertainty evaluation method. Among them, the measured value is the background radiation polarization response; the input quantity is the background radiation responsivity and temperature and other parameters. The evaluation of composite uncertainty u(B) is expressed by formula (6):

为输入量x_i的灵敏系数。In the formula, r( _xi , x _j ) is the correlation coefficient of input quantity x _i and x _j ,

It is the sensitivity coefficient of the input quantity x _i .

The advantages of the present invention are:

The background radiation measurement method based on the environmental simulation test is adopted. With the help of the fine adjustment function of the environmental simulation test system, the real working environment of the remote sensor is simulated, and the background radiation response is measured and calibrated, which effectively solves the problem of short-wave polarization caused by the background radiation. The increase of the background noise in the infrared band and the drift of the dynamic range reduce the influence of the background radiation on the measurement results of the short-wave infrared band of the polarization remote sensor.

Description of drawings

Fig. 1 is the background radiation test schematic diagram of the present invention;

Fig. 2 is the flow chart of background radiation correction method of the present invention;

Fig. 3 is the temperature control design flowchart of the vacuum high and low temperature environment simulation test system of the present invention;

Fig. 4 is a diagram of the background radiation correction effect in the short-wave infrared band of the polarization remote sensor of the present invention.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

The invention proposes a method for correcting the background radiation response of the polarization remote sensor in the short-wave infrared band, based on the relationship between the response of the polarization remote sensor in the short-wave infrared band and its absolute spectral responsivity, target spectral radiance, and background radiation response, and establishing the response of the polarization remote sensor function; divide the test temperature into multiple temperature levels, and use polynomial fitting to obtain the background radiation response of each channel; measure the background radiation response through the spectrally adjustable integrating sphere reference light source and vacuum high and low temperature environment simulation test system, and use the spectrally adjustable The spherical reference light source radiates to simulate the internal radiation of the instrument to obtain the equivalent black body temperature; use the ratio of the background radiation response signal at the known reference temperature to the background radiation equivalent spectral responsivity to obtain the corresponding in-band weighted radiance; use the evaluated weight The spectral radiance and the equivalent spectral responsivity of the internal radiation of the instrument are used to calculate the total response of the background radiation; the correction accuracy of the background radiation polarization response is analyzed by the method of composite uncertainty evaluation.

As shown in Figure 1, a kind of calibration device of the polarization remote sensor short-wave infrared band polarization calibration method based on background radiation correction of the present invention includes integrating sphere 1, vacuum high and low temperature environment simulation test system 2, spectral radiance meter 3, The short-wave infrared polarized remote sensor to be tested 4. The integrating sphere 1 is a light source, using bromine tungsten lamps, halogen tungsten lamps, white light lasers and other broadband light sources, and the spectral range can cover the short-wave infrared band. By using the spectral distribution characteristics of the integrating sphere, the calibration result is selected to verify the band interval. Validation of calibration results under different dynamic ranges of remote sensors. The temperature of the heat sink of the vacuum high and low temperature environment simulation test system 2 can be regulated, taking into account the high and low temperature test temperature and vacuum degree requirements of the thermal vacuum environment in different applications. The spectral radiance meter 3 is an integrating sphere radiance monitoring unit, the spectral range can cover the short-wave infrared band, and is used for monitoring the radiance value of the light source. The short-wave infrared polarization remote sensor 4 to be tested has a spectral range that can cover the short-wave infrared band, and is used for carrying out background radiation measurement experiments.

As shown in Figure 2, a method for correcting the background radiation response in the short-wave infrared band of the polarization remote sensor of the present invention specifically includes the following steps:

Step (1), according to the relationship between the short-wave infrared band response of the polarization remote sensor and its absolute spectral responsivity R(λ _k ), the target spectral radiance L(λ _k ), and the background radiation response F _bkg (λ _k ), the polarization The response function S(λ _k ) of the remote sensor is:

Among them, λ _k is the kth channel of the polarization remote sensor wavelength λ, k is the channel number of the polarization remote sensor, λ _min and λ _max are the shortest and longest wavelengths that the polarization remote sensor has response, L(λ _k ) is the wavelength λ The spectral radiance of the k-th channel, R(λ _k ) is the absolute spectral responsivity of the k-th channel at wavelength λ, and F _bkg (λ _k ) is the background radiation response of the k-th channel of the polarization remote sensor at wavelength λ.

In step (2), the test temperature of each channel of the polarization _remote sensor is divided into multiple temperature levels, and the background radiation response of _each channel is obtained by polynomial _fitting . _i ) means:

Among them, L _Int (λ _k ,t _i ) is the spectral radiance of the internal radiation of the instrument, R(λ _k ,t ₀ ) is the absolute spectral responsivity at the initial temperature point t ₀ , B _i is the fitting coefficient, t _i is the temperature point, and i is the number of the temperature point.

即辐射值；然后，将/>

按对应波段积分，获得该波段积分能量；最后，利用插值方法估算同等能量的黑体温度，如式(3)所示：Step (3), using the spectrally adjustable integrating sphere as the reference light source and the vacuum high and low temperature environment simulation test system to measure the background radiation response, using the spectrally adjustable integrating sphere as the reference light source to simulate the internal radiation of the instrument to obtain the equivalent black body temperature. First, the equivalent spectral responsivity of the internal radiation of the instrument is approximately calculated according to the original spectrum S _DS observed in the cold space, that is, the count value and the instrument spectral response function R(λ _k )

i.e. the radiation value; then, the />

Integrate according to the corresponding band to obtain the integral energy of the band; finally, use the interpolation method to estimate the blackbody temperature of the same energy, as shown in formula (3):

Among them, S _DS and S _ICT represent the output signal of the instrument when the cold space and the reference light source are incident, respectively, L _ICT represents the spectral radiance of the inner black body, R(λ _k ) is the spectral response function of the instrument, and <·> represents the mean value.

Step (4), using the temperature points of the vacuum high and low temperature environment simulation test system, the working environment temperature of the kth channel of the polarization remote sensor is divided into multiple temperature levels according to the actual working environment temperature changes, assuming that the temperature point is numbered as the temperature t of j _j is the known reference temperature, the ratio of the background radiation response signal F(λ _k ,t _j ) of the polarization remote sensor to the equivalent spectral responsivity of the background radiation at temperature t _j δ _bkg (λ _k ,t _j ) and the corresponding mth channel The in-band weighted radiance L _m (λ _j ) of is approximately equal, as shown in formula (4):

Step (5), using the weighted radiance L _m (λ _j ) corresponding to all known temperature points and the background radiation responsivity δ _bkg (λ _k ,t _j ), calculate the total background radiation response F _bkg (λ), as shown in the formula (5) as shown:

In step (6), the correction accuracy of the polarization response of the background radiation is analyzed by using the composite uncertainty evaluation method. According to the measurement method of the background radiation and the mathematical model B=f(x ₁ ,x ₂ …x _n ), determine the uncertainty u( _{xi )} and its propagation rate of the input quantity xi to the measurand, and combine the uncertainty The degree evaluation method is used to analyze the correction accuracy of background radiation polarization response. Among them, the measured value is the background radiation polarization response; the input quantity is the background radiation responsivity and temperature and other parameters. The evaluation of composite uncertainty u(B) is expressed by formula (6):

为输入量x_i的灵敏系数。In the formula, r( _xi , x _j ) is the correlation coefficient of input quantity x _i and x _j ,

It is the sensitivity coefficient of the input quantity x _i .

As shown in Figure 3, in order to achieve precise control of the stability and uniformity of the test environment temperature, a feedback automatic control method is adopted for temperature control, and a fuzzy adaptive fuzzy and P.I.D composite control mode is adopted. When the shape of the cavity and the radiation characteristics of the inner wall material are determined, the radiation energy is only related to the temperature. According to Stephen Boltzmann's law, the hemispherical full-wavelength radiation energy E of the actual object is:

E＝εσT ⁴ (7)

In the formula, ε is the specific emissivity, σ is the constant of proportionality, and T is the temperature.

After differentiating both sides, we get:

It can be known from formula (8) that the change of temperature will lead to the change of radiation energy. Therefore, in the Fuzzy and P.I.D compound feedback control algorithm, according to the characteristics of Fuzzy and PID control, in the dynamic process, use Fuzzy control, and when the system is close to or in the In steady state, it will automatically switch to P.I.D control.

As shown in FIG. 4 , it is an effect diagram of background radiation correction in the short-wave infrared band of the polarization remote sensor of the present invention.

The above descriptions are only specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. These examples are only for the purpose of illustration, and are not intended to limit the scope of the present invention. The scope of the invention is defined by the appended claims and their equivalents. Those skilled in the art can make various substitutions and modifications without departing from the scope of the present invention, and these substitutions and modifications should all fall within the scope of the present invention.

Claims (8)

1. A polarization remote sensor short-wave infrared band background radiation response correction method is characterized in that, comprising the following steps: Step (1), according to the relationship between the short-wave infrared band response of the polarization remote sensor and its absolute spectral responsivity R(λ _k ), the target spectral radiance L(λ _k ), and the background radiation response F _bkg (λ _k ), the polarization The response function S(λ _k ) of the remote sensor; In step (2), the test temperature of each channel of the polarization remote sensor is divided into multiple temperature levels, and polynomial fitting is used to obtain the background radiation response of each channel; Step (3), using the spectrally adjustable integrating sphere as the reference light source and the vacuum high and low temperature environment simulation test system to measure the background radiation response, using the spectrally adjustable integrating sphere as the reference light source to radiate the internal radiation of the simulated instrument to obtain the equivalent black body temperature; Step (4), using multiple temperature points of the vacuum high and low temperature environment simulation test system, under the condition of a known reference temperature, obtain the ratio of the background radiation response signal at the known reference temperature to the equivalent spectral responsivity of the background radiation Corresponding in-band weighted radiance L _m (λ _j ); Step (5), using the estimated weighted spectral radiance and the equivalent spectral responsivity of the internal radiation of the instrument to calculate the total background radiation response F _bkg (λ); In step (6), the correction accuracy of the polarization response of the background radiation is analyzed by using the composite uncertainty evaluation method. 2. a kind of polarized remote sensor short-wave infrared band background radiation response correction method according to claim 1, is characterized in that, in described step (1), the response function S (λ _k ) of described polarized remote sensor is:

Among them, λ _k is the kth channel of the polarization remote sensor wavelength λ, k is the channel number of the polarization remote sensor, λ _min and λ _max are the shortest and longest wavelengths that the polarization remote sensor has response, L(λ _k ) is the wavelength λ The spectral radiance of the k-th channel, R(λ _k ) is the absolute spectral responsivity of the k-th channel at wavelength λ, and F _bkg (λ _k ) is the background radiation response of the k-th channel of the polarization remote sensor at wavelength λ. 3. a kind of polarization remote sensor short-wave infrared band background radiation response correction method according to claim 2 is characterized in that, in described step (2), the background radiation response of each polarization channel of polarization remote sensor is divided into a plurality of temperature level, the background radiation response at temperature t _i is represented by F _bkg (λ _k , t _i ):

Among them, L _Int (λ _k ,t _i ) is the spectral radiance of the internal radiation of the instrument, R(λ _k ,t ₀ ) is the absolute spectral responsivity at the initial temperature point t ₀ , B _i is the fitting coefficient, t _i is the temperature point, and i is the number of the temperature point. 4. A kind of polarized remote sensor short-wave infrared band background radiation response correction method according to claim 3, it is characterized in that, described step (3) comprises: First, according to cold sky observation raw spectrum S _DS , namely count value and Approximate calculation of the equivalent spectral responsivity of the instrument's internal radiation by using the instrument's spectral response function R(λ _k )

i.e. the radiation value; then, the />

Integrate according to the corresponding band to obtain the integral energy of the band; finally, use the interpolation method to estimate the blackbody temperature of the same energy, as shown in formula (3):

Among them, S _DS and S _ICT represent the output signal of the instrument when the cold space and the reference light source are incident, respectively, L _ICT represents the spectral radiance of the inner black body, R(λ _k ) is the spectral response function of the instrument, and <·> represents the mean value. 5. a kind of polarization remote sensor short-wave infrared band background radiation response correction method according to claim 4 is characterized in that, described step (4) comprises: the working environment temperature of the kth channel of polarization remote sensor according to actual working environment The temperature change is divided into multiple temperature levels, assuming that the temperature t _j at the temperature point number j is a known reference temperature, the background radiation response signal F(λ _k , t _j ) of the polarized remote sensor and the equivalent spectrum of the background radiation at the temperature t _j The ratio of responsivity δ _bkg (λ _k ,t _j ) is approximately equal to the in-band weighted radiance L _m (λ _j ) corresponding to the mth channel, as shown in formula (4):

6. a kind of polarized remote sensor short-wave infrared band background radiation response correction method according to claim 5 is characterized in that, in described step (5), described background radiation total response F _bkg (λ _k ) is formed by all The weighted radiance Lm(λ _j ) corresponding to the known temperature point and the background radiation responsivity δ _bkg (λ _k ,t _j ) are expressed, as shown in formula (5):

7. a kind of polarization remote sensor short-wave infrared band background radiation response correcting method according to claim 6 is characterized in that, in described step (6), according to the measuring method of background radiation and mathematical model B=f(x ₁ ,x ₂ …x _n ), determine the uncertainty u( _xi ) and its transmission rate of the input quantity _xi to the measurand, and analyze the correction accuracy of the background radiation polarization response through the method of composite uncertainty evaluation; the measurand is the background radiation polarization response; the input is the background radiation responsivity and temperature and other parameters; the evaluation of the composite uncertainty u(B) is expressed by formula (6):

In the formula, r( _xi , x _j ) is the correlation coefficient of input quantity x _i and x _j ,

It is the sensitivity coefficient of the input quantity x _i . 8. a kind of polarization remote sensor short-wave infrared band background radiation response correcting method according to claim 3 is characterized in that, adopts feedback automatic control mode to carry out temperature control, adopts Fuzzy and P.I.D composite control mode of fuzzy self-adaptation; In the Fuzzy and P.I.D compound feedback control algorithm, according to the characteristics of Fuzzy and PID control, Fuzzy control is used in the dynamic process; when the system is close to or in a steady state, it is automatically switched to P.I.D control.

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